The present invention relates generally to the monitoring of the electrical voltage level available from power lines. More particularly, the present invention relates to a system for preventing electrical voltage from reaching an electrical system or appliance when the monitored electrical voltage is not within a predetermined range.
From time to time, the quality of electrical power provided to consumers by the local electric utility company varies from the 117 volts plus or minus 10% standard. For example, in order to cope with increased electrical loads during peak hours, such as, for example, in the evenings when electrical demand can be very high or during certain times of the year when there is a large demand for air conditioning or electrical heating, the voltage available to consumers can be reduced from the standard value. In particular, electric power utilities have been known to reduce the electrical voltage supplied to industrial users when they are experiencing high peak power usage.
Since most electrical systems and appliances designed for use in the United States are intended for use at the standard voltage of 117 volts, as the voltage varies from that value by more than the design standard deviation of 10%, damage to electrical appliances and systems, such as motors, condensers, microwave ovens and electrical appliances, can occur. In addition, for various reasons, electrical voltage spikes or surges are also unintentionally delivered to consumers. Such voltage spikes or surges can also damage or destroy electrical systems and consumer appliances, such as computers, stereos, microwave ovens, VCRs and the like by applying a voltage to those appliances which is higher than the appliance and/or the components of the appliance is designed to withstand.
One consumer area which is particularly sensitive to power voltage deviation conditions is that of recreational vehicle parks. Typically, such recreational vehicle parks provide spaces for parking recreational vehicles and trailers for a large number of users together with an electrical power outlet for each of the users. A similar set up is also utilized in marinas for boat owners.
Most recreational vehicle parks and marinas were built many years ago when users owned campers and small trailers (or small boats in the case of marinas). Since such recreational vehicle parks and marinas did not run at the same levels of capacity as today and the number of electrical systems and appliances used by such campers and small trailers or small boats was not as great as it is today, the electrical load when such recreational vehicle parks and marinas were designed was not as great as it is today. In addition, the electrical appliances and systems used today oftentimes contain complex electrical circuitry which requires greater voltage regulation.
Much of the time, the voltage provided to each of the users of these recreational vehicle parks and marinas is within the standard range of 117 volts plus or minus 10 percent. At certain times, such as during the peak hours of meal times or when heaters or air conditioners are being used, a great load is placed on the electrical power supply system. At those times, the voltage being supplied to each of the users can fall below that which is safe for use to properly operate recreational vehicle or boat appliances. In order to counter such an effect, some recreational vehicle parks and marinas will raise the voltage supplied to each of the spaces from its local transformer. When that happens and there is no load, that is, when very few recreational vehicles or boats are drawing electrical power, the voltage being supplied to each of the recreational vehicles may exceed the expected voltage range for which the recreational vehicle equipment was designed. In that case, severe damage to the electrical appliances in the recreational vehicle can result.
In order to try to prevent damage to electrical appliances in the recreational vehicles, many recreational vehicles have a voltmeter installed. However, in order to be effective, the voltmeter must be watched all of the time and then the user must take effective action to turn off the voltage being supplied to the recreational vehicle before damage to their electrical appliances, such as air conditioners, televisions, refrigerators, VCRs and converters, occurs. Such an approach is, however, totally unsatisfactory to users to implement.
Although the invention is described herein in connection with its use with recreational vehicles, it should be understood that its use is not to be limited to recreational vehicles and that it can be used to monitor electrical voltage applied to any load.